CLINICAL BACTERIOLOGY Flashcards
1
Q
- Each of the statements about the classification of streptococci is
correct EXCEPT:
(A) Pneumococci (Streptococcus pneumoniae) are α-hemolytic
and can be serotyped on the basis of their polysaccharide
capsules.
(B) Enterococci are group D streptococci and can be classified by
their ability to grow in 6.5% sodium chloride.
(C) Although pneumococci and the viridans streptococci are
α-hemolytic, they can be differentiated by the bile solubility
test and their susceptibility to optochin.
(D) Viridans streptococci are identified by Lancefield grouping,
which is based on the C carbohydrate in the cell wall.
A
(D) Viridans streptococci are identified by Lancefield grouping,
2
Q
54. Each of the following agents is a recognized cause of diarrhea EXCEPT: (A) Clostridium perfringens (B) Enterococcus faecalis (C) Escherichia coli (D) Vibrio cholerae
A
(B) Enterococcus faecalis
3
Q
55. Each of the following organisms is an important cause of urinary tract infections EXCEPT: (A) Escherichia coli (B) Proteus mirabilis (C) Klebsiella pneumoniae (D) Bacteroides fragilis
A
(D) Bacteroides fragilis
4
Q
- Your patient is a 30-year-old woman with nonbloody diarrhea
for the past 14 hours. Which one of the following organisms is
LEAST likely to cause this illness?
(A) Clostridium difficile
(B) Streptococcus pyogenes
(C) Shigella dysenteriae
(D) Salmonella enteritidis
A
(B) Streptococcus pyogenes
5
Q
- Each of the following statements concerning Mycobacterium
tuberculosis is correct EXCEPT:
(A) After being stained with carbolfuchsin, M. tuberculosis resists
decolorization with acid alcohol.
(B) Mycobacterium tuberculosis has a large amount of mycolic
acid in its cell wall.
(C) Mycobacterium tuberculosis appears as a red rod in Gramstained specimens.
(D) Mycobacterium tuberculosis appears as a red rod in acid-fast–
stained specimens
A
(C) Mycobacterium tuberculosis appears as a red rod in Gram stained specimens.
6
Q
59. Which one of the following diseases is BEST diagnosed by serologic means? (A) Q fever (B) Pulmonary tuberculosis (C) Gonorrhea (D) Actinomycosis
A
(A) Q fever
7
Q
- Your patient has subacute bacterial endocarditis caused by a
member of the viridans group of streptococci. Which one of the
following sites is MOST likely to be the source of the organism?
(A) Skin
(B) Colon
(C) Oropharynx
(D) Urethra
A
(C) Oropharynx
8
Q
- A culture of skin lesions from a patient with pyoderma (impetigo)
shows numerous colonies surrounded by a zone of β-hemolysis
on a blood agar plate. A Gram-stained smear shows gram-positive cocci. If you found the catalase test to be negative, which
one of the following organisms would you MOST probably have
isolated?
(A) Streptococcus pyogenes
(B) Staphylococcus aureus
(C) Staphylococcus epidermidis
(D) Streptococcus pneumoniae
A
(A) Streptococcus pyogenes
9
Q
- Which one of the following host defense mechanisms is the
MOST important for preventing dysentery caused by Salmonella?
(A) Gastric acid
(B) Salivary enzymes
(C) Normal flora of the mouth
(D) Alpha interfero
A
(A) Gastric acid
10
Q
66. Five hours after eating reheated rice at a restaurant, a 24-yearold woman and her husband both developed nausea, vomiting, and diarrhea. Which one of the following organisms is the MOST likely to be involved? (A) Clostridium perfringens (B) Enterotoxigenic Escherichia coli (C) Bacillus cereus (D) Salmonella typhi
A
(C) Bacillus cereus
11
Q
67. Which one of the following bacteria has the LOWEST 50% infectious dose (ID50)? (A) Shigella sonnei (B) Vibrio cholerae (C) Salmonella typhi (D) Campylobacter jejuni
A
(A) Shigella sonnei
12
Q
68. For which one of the following enteric illnesses is a chronic carrier state MOST likely to develop? (A) Campylobacter enterocolitis (B) Shigella enterocolitis (C) Cholera (D) Typhoid fever
A
(D) Typhoid fever
13
Q
69. Which one of the following zoonotic illnesses has NO arthropod vector? (A) Plague (B) Lyme disease (C) Brucellosis (D) Epidemic typhus
A
(C) Brucellosis
14
Q
- Which one of the following statements MOST accurately depicts
the ability of the organism to be cultured in the laboratory?
(A) Treponema pallidum from a chancre can be grown on a special artificial medium supplemented with cholesterol.
(B) Mycobacterium leprae can be grown in the armadillo and the
mouse footpad but not on any artificial media.
(C) Mycobacterium tuberculosis can be grown on enriched artificial media and produces visible colonies in 48 to 96 hours.
(D) Atypical mycobacteria are found widely in soil and water but
cannot be cultured on artificial media in the laboratory.
A
(B) Mycobacterium leprae can be grown in the armadillo and the
mouse footpad but not on any artificial media.
15
Q
- Each of the following statements concerning chlamydiae is correct EXCEPT:
(A) Chlamydiae are strict intracellular parasites because they
cannot synthesize sufficient adenosine triphosphate (ATP).
(B) Chlamydiae possess both DNA and RNA and are bounded
by a cell wall.
(C) Chlamydia trachomatis has multiple serotypes that can cause
different diseases.
(D) Most chlamydiae are transmitted by arthropods.
A
(D) Most chlamydiae are transmitted by arthropods.
16
Q
- For which one of the following bacterial vaccines are toxic side
effects an important concern?
(A) The vaccine containing pneumococcal polysaccharide
(B) The vaccine containing killed Bordetella pertussis
(C) The vaccine containing tetanus toxoid
(D) The vaccine containing diphtheria toxoid
A
(B) The vaccine containing killed Bordetella pertussis
17
Q
- A 65-year-old man develops dysuria and hematuria. A Gram
stain of a urine sample shows gram-negative rods. Culture of
the urine on EMB agar reveals lactose-negative colonies without evidence of swarming motility. Which one of the following
organisms is MOST likely to be the cause of his urinary tract
infection?
(A) Enterococcus faecalis
(B) Pseudomonas aeruginosa
(C) Proteus vulgaris
(D) Escherichia coli
A
(B) Pseudomonas aeruginosa
18
Q
77. A 25-year-old man complains of a urethral discharge. You perform a Gram stain on a specimen of the discharge and see neutrophils but no bacteria. Of the organisms listed, the one MOST likely to cause the discharge is: (A) Treponema pallidum (B) Chlamydia trachomatis (C) Candida albicans (D) Coxiella burnetii
A
(B) Chlamydia trachomatis
19
Q
- Your patient has a brain abscess that was detected 1 month after
a dental extraction. Which one of the following organisms is
MOST likely to be involved?
(A) Anaerobic streptococci
(B) Mycobacterium smegmatis
(C) Lactobacillus acidophilus
(D) Mycoplasma pneumoniae
A
(A) Anaerobic streptococci
20
Q
- The MOST important contribution of the capsule of Streptococcus
pneumoniae to virulence is:
(A) To prevent dehydration of the organisms on mucosal
surfaces
(B) To retard phagocytosis by polymorphonuclear leukocytes
(C) To inhibit polymorphonuclear leukocyte chemotaxis
(D) To accelerate tissue invasion by its collagenase-like activity
A
(B) To retard phagocytosis by polymorphonuclear leukocytes
21
Q
- The MOST important way the host counteracts the function of
the pneumococcal polysaccharide capsule is via:
(A) T lymphocytes sensitized to polysaccharide antigens
(B) Polysaccharide-degrading enzymes
(C) Anticapsular antibody
(D) Activated macrophages
A
(C) Anticapsular antibody
22
Q
- The pathogenesis of which one of the following organisms is
MOST likely to involve invasion of the intestinal mucosa?
(A) Vibrio cholerae
(B) Shigella sonnei
(C) Enterotoxigenic Escherichia coli
(D) Clostridium botulinum
A
(B) Shigella sonnei
23
Q
83. Which one of the following organisms that infects the gastrointestinal tract is the MOST frequent cause of bacteremia? (A) Shigella flexneri (B) Campylobacter jejuni (C) Vibrio cholerae (D) Salmonella typhi
A
(D) Salmonella typhi
24
Q
- Each of the following statements concerning Treponema is correct EXCEPT:
(A) Treponema pallidum produces an exotoxin that stimulates
adenylate cyclase.
(B) Treponema pallidum cannot be grown on conventional laboratory media.
(C) Treponemes are members of the normal flora of the human
oropharynx.
(D) Patients infected with T. pallidum produce antibodies that
react with beef heart cardiolipin.
A
(A) Treponema pallidum produces an exotoxin that stimulates
adenylate cyclase.
25
Q
- A 70-year-old man is found to have a hard mass in his prostate, which is suspected to be a carcinoma. Twenty-four hours
after surgical removal of the mass, he develops fever to 39°C and
has several shaking chills. Of the organisms listed, which one is
LEAST likely to be involved?
(A) Escherichia coli
(B) Enterococcus faecalis
(C) Klebsiella pneumoniae
(D) Legionella pneumophila
A
(D) Legionella pneumophila
26
Q
93. The pathogenesis of which one of the following diseases does NOT involve an exotoxin? (A) Scarlet fever (B) Typhoid fever (C) Toxic shock syndrome (D) Botulism
A
(B) Typhoid fever
27
Q
94. Regarding the effect of benzylpenicillin (penicillin G) on bacteria, which one of the following organisms is LEAST likely to be resistant? (A) Staphylococcus aureus (B) Enterococcus faecalis (C) Streptococcus pyogenes (D) Neisseria gonorrhoeae
A
(C) Streptococcus pyogenes
28
Q
- Which one of the following organisms is MOST likely to be the
cause of pneumonia in an immunocompetent young adult?
(A) Nocardia asteroides
(B) Serratia marcescens
(C) Mycoplasma pneumoniae
(D) Legionella pneumophila
A
(C) Mycoplasma pneumoniae
29
Q
- Each of the following statements concerning chlamydial genital
tract infections is correct EXCEPT:
(A) Infection can be diagnosed by finding antichlamydial antibody in a serum specimen.
(B) Infection can persist after administration of penicillin.
(C) Symptomatic infections can be associated with urethral or
cervical discharge containing many polymorphonuclear
leukocytes.
(D) There is no vaccine against these infections.
A
(A) Infection can be diagnosed by finding antichlamydial antibody in a serum specimen.
30
Q
97. Which one of the following illnesses is NOT a zoonosis? (A) Typhoid fever (B) Q fever (C) Tularemia (D) Rocky Mountain spotted fever
A
(A) Typhoid fever
31
Q
- Which one of the following is NOT an important characteristic
of either Neisseria gonorrhoeae or Neisseria meningitidis?
(A) Polysaccharide capsule
(B) IgA protease
(C) M protein
(D) Pili
A
(C) M protein
32
Q
- Which one of the following is NOT an important characteristic
of Streptococcus pyogenes?
(A) Protein A
(B) M protein
(C) β-Hemolysin
(D) Polysaccharide group-specific substance
A
(A) Protein A
33
Q
- Each of the following is associated with the Lancefield group B
streptococci (S. agalactiae) EXCEPT:
(A) Pyoderma (impetigo)
(B) Vaginal carriage in 5% to 25% of normal women of childbearing age
(C) Neonatal sepsis and meningitis
(D) β-Hemolysis
A
(A) Pyoderma (impetigo)
34
Q
102. Three organisms, Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae, cause the vast majority of cases of bacterial meningitis. What is the MOST important pathogenic component they share? (A) Protein A (B) Capsule (C) Endotoxin (D) β-Lactamase
A
(B) Capsule
35
Q
103. Diarrhea caused by which one of the following agents is characterized by the presence of fecal leukocytes? (A) Campylobacter jejuni (B) Rotavirus (C) Clostridium perfringens (D) Enterotoxigenic Escherichia coli
A
(A) Campylobacter jejuni
36
Q
- Each of the following statements concerning Chlamydia
trachomatis is correct EXCEPT:
(A) It is an important cause of nongonococcal urethritis.
(B) It is the cause of lymphogranuloma venereum.
(C) It is an important cause of subacute bacterial endocarditis.
(D) It is an important cause of conjunctivitis.
A
(C) It is an important cause of subacute bacterial endocarditis.
37
Q
106. Which one of the following types of organisms is NOT an obligate intracellular parasite and therefore can replicate on bacteriologic media? (A) Chlamydia (B) Mycoplasma (C) Adenovirus (D) Rickettsia
A
(B) Mycoplasma
38
Q
- Tissue-degrading enzymes play an important role in the pathogenesis of several bacteria. Which one of the following is NOT
involved in tissue or cell damage?
(A) Lecithinase of Clostridium perfringens
(B) Hyaluronidase of Streptococcus pyogenes
(C) M protein of Streptococcus pneumoniae
(D) Leukocidin of Staphylococcus aureus
A
(C) M protein of Streptococcus pneumoniae
39
Q
- The soil is the natural habitat for certain microorganisms of
medical importance. Which one of the following is LEAST likely
to reside there?
(A) Clostridium tetani
(B) Mycobacterium avium-intracellulare
(C) Bacillus anthracis
(D) Chlamydia trachomatis
A
(D) Chlamydia trachomatis
40
Q
109. Which one of the following organisms is the MOST frequent bacterial cause of pharyngitis? (A) Staphylococcus aureus (B) Streptococcus pneumoniae (C) Streptococcus pyogenes (D) Neisseria meningitidis
A
(C) Streptococcus pyogenes
41
Q
- Several pathogens are transmitted either during gestation or at
birth. Which one of the following is LEAST likely to be transmitted at these times?
(A) Haemophilus influenzae
(B) Treponema pallidum
(C) Neisseria gonorrhoeae
(D) Chlamydia trachomatis
A
(A) Haemophilus influenzae
42
Q
- Each of the following statements concerning the VDRL test for
syphilis is correct EXCEPT:
(A) The antigen is composed of inactivated Treponema
pallidum.
(B) The test is usually positive in secondary syphilis.
(C) False-positive results are more frequent than with the fluorescent treponemal antibody-absorbed (FTA-ABS) test.
(D) The antibody titer declines with appropriate therapy.
A
(A) The antigen is composed of inactivated Treponema
pallidum.
43
Q
- Each of the following statements concerning the fluorescent
treponemal antibody-absorbed (FTA-ABS) test for syphilis is
correct EXCEPT:
(A) The test is specific for Treponema pallidum.
(B) The patient’s serum is absorbed with saprophytic
treponemes.
(C) Once positive, the test remains so despite appropriate
therapy.
(D) The test is rarely positive in primary syphilis.
A
(D) The test is rarely positive in primary syphilis.
44
Q
- Each of the following statements concerning enterotoxins is correct EXCEPT:
(A) Enterotoxins typically cause bloody diarrhea with leukocytes
in the stool.
(B) Staphylococcus aureus produces an enterotoxin that causes
vomiting and diarrhea.
(C) Vibrio cholerae causes cholera by producing an enterotoxin
that increases adenylate cyclase activity within the enterocyte.
(D) Escherichia coli enterotoxin mediates ADP-ribosylation of a
G protein.
A
(A) Enterotoxins typically cause bloody diarrhea with leukocytes
in the stool.
45
Q
- Each of the following statements concerning plague is correct
EXCEPT:
(A) Plague is caused by a gram-negative rod that can be cultured
on blood agar.
(B) Plague is transmitted from the animal reservoir to humans
by flea bite.
(C) The main reservoirs in nature are small rodents.
(D) Plague is of concern in many underdeveloped countries but
has not occurred in the United States since 1968.
A
(D) Plague is of concern in many underdeveloped countries but
has not occurred in the United States since 1968.
46
Q
- Which one of the following statements concerning the organisms that cause brucellosis is CORRECT?
(A) Brucellae are transmitted primarily by tick bite.
(B) The principal reservoirs of Brucellae are small rodents.
(C) Brucellae infect reticuloendothelial cells in the liver, spleen,
and bone marrow.
(D) Brucellae are obligate intracellular parasites that are usually
identified by growth in human cell culture.
A
(C) Brucellae infect reticuloendothelial cells in the liver, spleen,
and bone marrow
47
Q
120. Which one of the following organisms causes diarrhea by producing an enterotoxin that increases adenylate cyclase activity within enterocytes? (A) Escherichia coli (B) Bacteroides fragilis (C) Staphylococcus aureus (D) Enterococcus faecalis
A
(A) Escherichia coli
48
Q
- Each of the following statements concerning gonorrhea is correct EXCEPT:
(A) Infection in men is more frequently symptomatic than in
women.
(B) A presumptive diagnosis can be made by finding gramnegative kidney bean-shaped diplococci within neutrophils
in a urethral discharge.
(C) The definitive diagnosis can be made by detecting antibodies
to Neisseria gonorrhoeae in the patient’s serum.
(D) Gonococcal conjunctivitis of the newborn rarely occurs in
the United States, because silver nitrate or erythromycin is
commonly used as prophylaxis.
A
(C) The definitive diagnosis can be made by detecting antibodies
to Neisseria gonorrhoeae in the patient’s serum.
49
Q
- Each of the following statements concerning spirochetes is correct EXCEPT:
(A) Species of Treponema are part of the normal flora of the
mouth.
(B) Species of Borrelia cause a tick-borne disease called relapsing
fever.
(C) The species of Leptospira that cause leptospirosis grow primarily in humans and are usually transmitted by human-tohuman contact.
(D) Species of Treponema cause syphilis and yaws.
A
(C) The species of Leptospira that cause leptospirosis grow primarily in humans and are usually transmitted by human-tohuman contact.
50
Q
- Each of the following statements concerning Mycobacterium
tuberculosis is correct EXCEPT:
(A) Some strains of M. tuberculosis isolated from patients exhibit
multiple drug resistance (i.e., they are resistant to both isoniazid and rifampin).
(B) Mycobacterium tuberculosis contains a small amount of lipid
in its cell wall and therefore stains poorly with the Gram
stain.
(C) Mycobacterium tuberculosis grows slowly, often requiring 3
to 6 weeks before colonies appear.
(D) The antigen in the tuberculin skin test is a protein extracted
from the organism.
A
(B) Mycobacterium tuberculosis contains a small amount of lipid
in its cell wall and therefore stains poorly with the Gram
stain.
51
Q
- Each of the following statements concerning neisseriae is correct EXCEPT:
(A) They are gram-negative diplococci.
(B) They produce IgA protease as a virulence factor.
(C) They are oxidase-positive.
(D) They grow best under anaerobic conditions.
A
(D) They grow best under anaerobic conditions.
52
Q
- Which one of the following statements concerning Legionella
pneumophila is CORRECT?
(A) It is part of the normal flora of the colon.
(B) It cannot be grown on laboratory media.
(C) It does not have a cell wall.
(D) It causes atypical pneumonia, especially in those with
reduced cell-mediated immunity.
A
(D) It causes atypical pneumonia, especially in those with
reduced cell-mediated immunity.
53
Q
- Each of the following statements concerning infection with
Chlamydia psittaci is correct EXCEPT:
(A) Chylamydia psittaci can be isolated by growth in cell culture
and will not grow in blood agar.
(B) The organism appears purple in Gram-stained smears of
sputum.
(C) The infection is more readily diagnosed by serologic tests
than by isolation of the organism.
(D) The infection is more commonly acquired from a nonhuman
source than from another human.
A
(B) The organism appears purple in Gram-stained smears of
sputum.
54
Q
132. Ticks are vectors for the transmission of each of the following diseases EXCEPT: (A) Rocky Mountain spotted fever (B) Epidemic typhus (C) Tularemia (D) Lyme disease
A
(B) Epidemic typhus
55
Q
- Each of the following statements concerning pneumonia caused
by Mycoplasma pneumoniae is correct EXCEPT:
(A) Pneumonia caused by M. pneumoniae is associated with a
rise in the titer of cold agglutinins.
(B) Pneumonia caused by M. pneumoniae occurs primarily in
immunocompetent individuals.
(C) Pneumonia caused by M. pneumoniae is an “atypical”
pneumonia.
(D) Mycoplasma pneumoniae cannot be cultured in vitro because
it has no cell wall.
A
(D) Mycoplasma pneumoniae cannot be cultured in vitro because
it has no cell wall.
56
Q
- Each of the following statements concerning Neisseria
meningitidis is correct EXCEPT:
(A) It is an oxidase-positive, gram-negative diplococcus.
(B) It contains endotoxin in its cell wall.
(C) It produces an exotoxin that stimulates adenylate cyclase.
(D) It has a polysaccharide capsule that is antiphagocytic.
A
(C) It produces an exotoxin that stimulates adenylate cyclase.
57
Q
- Each of the following statements concerning Mycobacterium
leprae is correct EXCEPT:
(A) In lepromatous leprosy, large numbers of organisms are usually seen in acid-fast–stained smears.
(B) The organism will grow on bacteriologic media in 3 to 6 weeks.
(C) Prolonged therapy (9 months or longer) is required to prevent recurrence.
(D) Loss of sensation due to nerve damage is often seen in leprosy.
A
(B) The organism will grow on bacteriologic media in 3 to 6 weeks.
58
Q
- An outbreak of sepsis caused by Staphylococcus aureus has
occurred in the newborn nursery. You are called upon to investigate. According to your knowledge of the normal flora, what is
the MOST likely source of the organism?
(A) Colon
(B) Nose
(C) Throat
(D) Vagina
A
(B) Nose
59
Q
- A 50-year-old homeless alcoholic has a fever and is coughing up
1 cup of green, foul-smelling sputum per day. You suspect that
he may have a lung abscess. Which one of the following pairs of
organisms is MOST likely to be the cause?
(A) Listeria monocytogenes and Legionella pneumophila
(B) Nocardia asteroides and Mycoplasma pneumoniae
(C) Fusobacterium nucleatum and Peptostreptococcus
intermedius
(D) Clostridium perfringens and Chlamydia psittaci
A
(C) Fusobacterium nucleatum and Peptostreptococcus
intermedius
60
Q
- The coagulase test, in which the bacteria cause plasma to clot, is
used to distinguish:
(A) Streptococcus pyogenes from Enterococcus faecalis
(B) Streptococcus pyogenes from Staphylococcus aureus
(C) Staphylococcus aureus from Staphylococcus epidermidis
(D) Staphylococcus epidermidis from Neisseria meningitidis
A
(C) Staphylococcus aureus from Staphylococcus epidermidis
61
Q
- Which one of the following is a virulence factor for Staphylococcus
aureus?
(A) A heat-labile toxin that inhibits glycine release at the internuncial neuron
(B) An oxygen-labile hemolysin
(C) Resistance to novobiocin
(D) Protein A that binds to the Fc portion of IgG
A
(D) Protein A that binds to the Fc portion of IgG
62
Q
- The MOST important protective function of the antibody stimulated by tetanus immunization is:
(A) To opsonize the pathogen (Clostridium tetani)
(B) To prevent growth of the pathogen
(C) To prevent adherence of the pathogen
(D) To neutralize the toxin of the pathogen
A
(D) To neutralize the toxin of the pathogen
63
Q
70. Which one of the following organisms principally infects vascular endothelial cells and as a result often causes a petechial rash? (A) Salmonella typhi (B) Rickettsia rickettsii (C) Haemophilus influenzae (D) Coxiella burnetii
A
(B) Rickettsia rickettsii
64
Q
- Each of the following statements concerning Staphylococcus
aureus is correct EXCEPT:
(A) Gram-positive cocci in grapelike clusters are seen on Gramstained smear.
(B) The coagulase test is positive.
(C) Treatment should include a β-lactamase-resistant penicillin.
D) Endotoxin is an important pathogenetic factor
A
D) Endotoxin is an important pathogenetic factor
65
Q
- Your patient is a 70-year-old man who underwent bowel surgery
for colon cancer 3 days ago. He now has a fever and abdominal
pain. You are concerned that he may have peritonitis. Which
one of the following pairs of organisms is MOST likely to be the
cause?
(A) Bacteroides fragilis and Klebsiella pneumoniae
(B) Bordetella pertussis and Salmonella enteritidis
(C) Actinomyces israelii and Campylobacter jejuni
(D) Clostridium botulinum and Shigella dysenteriae
A
(A) Bacteroides fragilis and Klebsiella pneumoniae
66
Q
- Two hours after a delicious Thanksgiving dinner of barley soup,
roast turkey, stuffing, sweet potato, green beans, cranberry sauce,
and pumpkin pie topped with whipped cream, the Smith family
of four experience vomiting and diarrhea. Which one of the following organisms is MOST likely to cause these symptoms?
(A) Shigella flexneri
(B) Campylobacter jejuni
(C) Staphylococcus aureus
(D) Salmonella enteritidis
A
(C) Staphylococcus aureus
67
Q
- Each of the following statements concerning clostridia is correct
EXCEPT:
(A) Pathogenic clostridia are found both in the soil and in the
normal flora of the colon.
(B) Antibiotic-associated (pseudomembranous) colitis is due to
a toxin produced by Clostridium difficile.
(C) Anaerobic conditions at the wound site are not required to
cause tetanus, because spores will form in the presence of
oxygen.
(D) Botulism, which is caused by ingesting preformed toxin, can
be prevented by boiling food prior to eating.
A
(C) Anaerobic conditions at the wound site are not required to
cause tetanus, because spores will form in the presence of
oxygen.
68
Q
- Each of the following statements concerning Bacteroides fragilis
is correct EXCEPT:
(A) Bacteroides fragilis is a gram-negative rod that is part of the
normal flora of the colon.
(B) Bacteroides fragilis forms endospores, which allow it to survive in the soil.
(C) The capsule of B. fragilis is an important virulence factor.
(D) Bacteroides fragilis infections are characterized by foulsmelling pus.
A
(B) Bacteroides fragilis forms endospores, which allow it to survive in the soil.
69
Q
- Each of the following statements concerning staphylococci is
correct EXCEPT:
(A) Staphylococcus aureus is differentiated from Staphylococcus
epidermidis by the production of coagulase.
(B) Staphylococcus aureus infections are often associated with
abscess formation.
(C) The majority of clinical isolates of S. aureus produce penicillinase; therefore, penicillin G should not be used for antibiotic therapy for S. aureus infections.
(D) Scalded skin syndrome caused by S. aureus is due to enzymatic degradation of epidermal desmosomes by catal
A
(D) Scalded skin syndrome caused by S. aureus is due to enzymatic degradation of epidermal desmosomes by catal
70
Q
- Five days ago, a 65-year-old woman with a lower urinary tract
infection began taking ampicillin. She now has a fever and
severe diarrhea. Of the organisms listed, which one is MOST
likely to be the cause of the diarrhea?
(A) Clostridium difficile
(B) Bacteroides fragilis
(C) Proteus mirabilis
(D) Bordetella pertussis
A
(A) Clostridium difficile
71
Q
- Which one of the following is NOT a characteristic of the
Staphylococcus associated with toxic shock syndrome?
(A) Release of a superantigen
(B) Coagulase production
(C) Appearance of the organism in grapelike clusters on Gramstained smear
(D) Catalase-negative reaction
A
(D) Catalase-negative reaction
72
Q
- Each of the following statements concerning Actinomyces and
Nocardia is correct EXCEPT:
(A) Actinomysis israelii is an anaerobic rod found as part of the
normal flora in the mouth.
(B) Both Actinomyces and Nocardia are branching, filamentous
rods.
(C) Nocardia asteroides causes infections primarily in immunocompromised patients.
(D) Infections are usually diagnosed by detecting a significant
rise in antibody titer.
A
(D) Infections are usually diagnosed by detecting a significant
rise in antibody titer.
73
Q
- Each of the following statements concerning exotoxins is correct
EXCEPT:
(A) Some strains of Escherichia coli produce an enterotoxin that
causes diarrhea.
(B) Cholera toxin acts by stimulating adenylate cyclase.
(C) Diphtheria is caused by an exotoxin that inhibits protein
synthesis by inactivating an elongation factor.
(D) Botulism is caused by a toxin that hydrolyzes lecithin
(lecithinase), thereby destroying nerve cells.
A
(D) Botulism is caused by a toxin that hydrolyzes lecithin
(lecithinase), thereby destroying nerve cells.
74
Q
- Each of the following statements concerning Corynebacterium
diphtheriae is correct EXCEPT:
(A) Corynebacterium diphtheriae is a gram-positive rod that does
not form spores.
(B) Toxin production is dependent on the organism’s being
lysogenized by a bacteriophage.
(C) Diphtheria toxoid should not be given to children younger
than 3 years because the incidence of complications is too
high.
(D) Antitoxin should be used to treat patients with diphtheria.
A
(C) Diphtheria toxoid should not be given to children younger
than 3 years because the incidence of complications is too
high.
75
Q
- Each of the following statements concerning epidemic typhus is
correct EXCEPT:
(A) The disease is characterized by a rash.
(B) The Weil-Felix test can aid in diagnosis of the disease.
(C) The disease is caused by a Rickettsia.
(D) The causative organism is transmitted from rodents to
humans by a tick.
A
(D) The causative organism is transmitted from rodents to
humans by a tick.
76
Q
- Each of the following statements concerning Rocky Mountain
spotted fever is correct EXCEPT:
(A) The causative organism forms β-hemolytic colonies on blood
agar.
(B) Headache, fever, and rash are characteristic features of the
disease.
(C) The disease occurs primarily east of the Mississippi.
(D) The disease is caused by a Rickettsia.
A
(A) The causative organism forms β-hemolytic colonies on blood
agar.
77
Q
- Each of the following statements concerning Clostridium
perfringens is correct EXCEPT:
(A) It causes gas gangrene.
(B) It causes food poisoning.
(C) It produces an exotoxin that degrades lecithin and causes
necrosis and hemolysis.
(D) It is a gram-negative rod that does not ferment lactose.
A
(D) It is a gram-negative rod that does not ferment lactose.
78
Q
- Each of the following statements concerning Clostridium tetani
is correct EXCEPT:
(A) It is a gram-positive, spore-forming rod.
(B) Pathogenesis is due to the production of an exotoxin that
blocks inhibitory neurotransmitters.
(C) It is a facultative organism; it will grow on a blood agar plate
in the presence of room air.
(D) Its natural habitat is primarily the soil.
A
(C) It is a facultative organism; it will grow on a blood agar plate
in the presence of room air.
79
Q
- Which one of the following statements concerning immunization against diseases caused by clostridia is CORRECT?
(A) Antitoxin against tetanus protects against botulism as well,
because the two toxins share antigenic sites.
(B) Vaccines containing alpha toxin (lecithinase) are effective in
protecting against gas gangrene.
(C) The toxoid vaccine against Clostridium difficile infection
should be administered to immunocompromised patients.
(D) Immunization with tetanus toxoid induces effective protection against tetanus toxin.
A
(D) Immunization with tetanus toxoid induces effective protection against tetanus toxin.
80
Q
- Each of the following statements concerning wound infections
caused by Clostridium perfringens is correct EXCEPT:
(A) An exotoxin plays a role in pathogenesis.
(B) Gram-positive rods are found in the exudate.
(C) The organism grows only in human cell culture.
(D) Anaerobic culture of the wound site should be ordered.
A
(C) The organism grows only in human cell culture.
81
Q
- Each of the following statements concerning Q fever is correct
EXCEPT:
(A) Rash is a prominent feature.
(B) It is transmitted by respiratory aerosol.
(C) Farm animals are an important reservoir.
(D) It is caused by Coxiella burnetii.
A
(A) Rash is a prominent feature.
